Reducing cooling tube bursts in electronic devices

ABSTRACT

Embodiments of the present invention can reduce the chances of tube bursts in electronic devices by using tubes with cross-sectional shapes that can be deformed into larger cross-sectional areas to accommodate coolant expansion due to freezing with little or no corresponding increase in the perimeter length of the cross-section.

FIELD OF THE INVENTION

The present invention relates to the field of electronics. More specifically, the present invention relates to reducing cooling tube bursts in electronic devices.

BACKGROUND

Components in electronic devices continue to get smaller and faster as more and more transistors are packed into each new generation of integrated circuit (IC) chip. These components can generate a great deal of heat, and the amount of heat tends to increase as the components get smaller and faster. In order to work properly, however, the components cannot get too hot.

In the past, most electronic devices were entirely air-cooled with heat sinks and fans. But, fluid-cooled systems are being increasingly used. In a typical fluid-cooled system, a fluid coolant circulates through tubes among a heat exchanger and one or more components in an electronic device. The fluid can absorb heat from the component(s) and dissipate the heat at the heat exchanger.

Fluid-cooled systems can provide a variety of advantages over air-cooled systems. For example, a fluid-cooled system may dissipate a great deal more heat than an air cooled system. And, a fluid-cooled system often allows more flexibility in the size and dimensions of electronic devices because a heat exchanger can be located remotely from heat-producing components, as opposed to heat sinks and fans which often need to be located in very close proximity to heat-producing components.

One potential disadvantage of fluid-cooled systems is the potential for tube bursts. An electronic device may be subjected to very low ambient temperatures at which a coolant might freeze. If the coolant is a substance that expands when it freezes, such as water, the expansion may burst a tube.

BRIEF DESCRIPTION OF DRAWINGS

Examples of the present invention are illustrated in the accompanying drawings. The accompanying drawings, however, do not limit the scope of the present invention. Similar references in the drawings indicate similar elements.

FIG. 1 illustrates one embodiment of an electronic device.

FIG. 2 illustrates one embodiment of a cooling tube.

FIG. 3 illustrates various embodiment of cooling tube cross-sections.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, those skilled in the art will understand that the present invention may be practiced without these specific details, that the present invention is not limited to the depicted embodiments, and that the present invention may be practiced in a variety of alternative embodiments. In other instances, well known methods, procedures, components, and circuits have not been described in detail.

Parts of the description will be presented using terminology commonly employed by those skilled in the art to convey the substance of their work to others skilled in the art. Various operations will be described as multiple discrete steps performed in turn in a manner that is helpful for understanding the present invention. However, the order of description should not be construed as to imply that these operations are necessarily performed in the order they are presented, nor even order dependent. Lastly, repeated usage of the phrase “in one embodiment” does not necessarily refer to the same embodiment, although it may.

Embodiments of the present invention can reduce the chances of tube bursts in electronic devices by using tubes with cross-sectional shapes that can be deformed into larger cross-sectional areas to accommodate coolant expansion due to freezing with little or no corresponding increase in the perimeter length of the cross-section.

FIG. 1 illustrates one embodiment of an electronic device 100 in which an embodiment of the present invention can be used. Electronic device 100 includes a printed circuit board (PCB) 110 to which a processor 120, a heat exchanger 130, and a pump 150 are attached. A fluid coolant can be circulated by pump 150 between processor 120 and heat exchanger 130 through cooling tubes 140.

Electronic device 100 is intended to represent a wide variety of electronic devices including, for instance, desktop computers, laptop computers, tablet computers, personal data assistants (PDAs), telephones, and any other kind of electronic device in which fluid-cooling can be used. Processor 120 is intended to represent a wide variety of heat-producing electronic components for which fluid-cooling can be used, including, for instance, digital signal processors (DSPs), multi-core processors, and the like. Heat exchanger 130 is intended to represent any of a number of heat exchanging devices including, for instance, a radiator with a heat sink and/or fan. Other embodiments of electronic device 100 may include additional components, additional heat exchangers, and/or additional cooling tubes, and all of the components can be arranged and coupled in any of a variety of ways. In alternate embodiments, the cooling tube could be a heat pipe. In which case, no pump would be needed because coolant can be circulated through a heat pipe by the heating and cooling the coolant itself.

In the illustrated embodiment, the fluid-cooling system could be a single-phase system. That is, the coolant may remain in a liquid form during normal operation. Alternately, the system could be a two-phase system in which the coolant is vaporized or partially vaporized in normal operation as it absorbs heat and is returned to liquid when it dissipates heat.

Any of a number of coolants can be used. Coolants that expand when frozen, however, such as water and certain liquid metals, can cause tube bursts in either kind of system. Tube bursts may be less common in two-phase systems because the liquid coolant usually does not completely fill the tubes, leaving room for expansion due to freezing. A single phase system tends to fill much more of the volume in the tubes, making expansion more problematic. But, even in a two-phase system, portions of a tube can be substantially filled with coolant. In which case, non-uniform freezing can trap the coolant and cause a burst.

Both kinds of cooling systems may operate under varying amounts of pressure during normal circumstances as the average temperature of the coolant increases and decreases. In which case, the cooling tubes 140 are often fairly rigid to substantially maintain the overall volume of the cooling system during operation. The expansion pressure that can be exerted on the tubes as a coolant freezes, however, can be considerably higher.

Many coolants may expand when they freeze. Water, for instance, expands about 8% as it freezes. Embodiments of the present invention can provide for this change in volume using tubes with non-circular cross-sections. The tubes can deform into larger cross-sectional forms under the high expansion pressures of freezing while still substantially maintaining the perimeter length of the tubing. This can result in an overall lower amount of stress in the tube wall upon freezing.

FIG. 2 illustrates one embodiment of an inventive cooling tube 140 in two different states. Tube 140 has a fluid channel 210 formed by wall 220. When fluid channel 210 contains liquid coolant 240, wall 220 is in a relaxed state 230, having an elliptical cross-sectional shape. On the other hand, when fluid channel 210 is filled with frozen coolant 250, wall 220 can deform into expanded state 260.

In the illustrated embodiment, wall 220 is substantially circular when in expanded state 260. Even if the perimeter of the cross-sectional shape does not change from state 230 to state 260, the area will increase as the cross-section becomes more circular. Assuming the coolant is water and the area can increase by at least 8%, cooling tube 140 may not burst due to freezing.

Tube 140 can be made from any of a variety of materials including plastics and metals. In certain embodiments, the material may be rigid enough to maintain its shape under regular operating pressures, yet deform under the expansion pressure from freezing. In the illustrated embodiment, wall 220 comprises an elastic material so that tube 140 can return to relaxed state 230 as the coolant melts. If the material deforms in the elastic regime, tube 140 may be able to transition between states many times without bursting.

Alternate embodiments can use a wide variety of non-circular cross-sections. FIG. 3 illustrates a few possibilities. The first cross-sectional shapes 310 on the left side are in the relaxed state, including square, rectangular, triangular, and trapezoidal cross-sections. The second cross-sectional shapes 320 on the right side illustrate how each shape may deform in the expanded state. In each case, the sides bulge out and the corners draw in, resulting in a overall increase from the relaxed area 350 to the expanded area 360, even if the relaxed perimeter remains substantially equal to the expanded perimeter.

Thus, reducing cooling tube bursts in electronic devices is described. Whereas many alterations and modifications of the present invention will be comprehended by a person skilled in the art after having read the foregoing description, it is to be understood that the particular embodiments shown and described by way of illustration are in no way intended to be considered limiting. Therefore, references to details of particular embodiments are not intended to limit the scope of the claims. 

1. A cooling tube for use in an electronic device, the cooling tube comprising: a fluid channel to carry a coolant to cool the electronic device; and a wall to form the fluid channel, said wall having a first cross-sectional shape when in a relaxed state and a second cross-sectional shape when in an expanded state, the second cross-sectional shape having a larger area than the first cross-sectional shape.
 2. The cooling tube of claim 1 wherein the coolant comprises one of water or liquid metal.
 3. The cooling tube of claim 1 wherein the electronic device comprises a processor.
 4. The cooling tube of claim 1 wherein the first cross-sectional shape is non-circular.
 5. The cooling tube of claim 1 wherein the second cross-sectional shape is more circular than the first cross-sectional shape.
 6. The cooling tube of claim 1 wherein the first cross-sectional shape is one of elliptical, square, rectangular, triangular, or trapezoidal.
 7. The cooling tube of claim 1 wherein a difference in an area of the first cross-sectional shape and an area of the second cross-sectional shape is at least 8%.
 8. The cooling tube of claim 1 wherein a perimeter of the first cross-sectional shape is substantially equal to a perimeter of the second cross-sectional shape.
 9. The cooling tube of claim 1 wherein the wall operates in the elastic regime to transition repeatedly between the first cross-sectional shape and the second cross-sectional shape.
 10. A system comprising: a processor; a heat exchanger; and a cooling tube to couple the processor and the heat exchanger, the cooling tube comprising: a fluid channel to carry a coolant; and a wall to form the fluid channel, said wall having a first cross-sectional shape when in a relaxed state and a second cross-sectional shape when in an expanded state, the second cross-sectional shape having a larger area than the first cross-sectional shape.
 11. The system of claim 10 wherein the coolant comprises one of water or liquid metal.
 12. The system of claim 10 wherein the first cross-sectional shape is non-circular.
 13. The system of claim 10 wherein the second cross-sectional shape is more circular than the first cross-sectional shape.
 14. The system of claim 10 wherein the first cross-sectional shape is one of elliptical, square, rectangular, triangular, or trapezoidal.
 15. The system of claim 10 wherein a difference in an area of the first cross-sectional shape and an area of the second cross-sectional shape is at least 8%.
 16. The system of claim 10 wherein a circumference of the first cross-sectional shape is substantially equal to a circumference of the second cross-sectional shape.
 17. The system of claim 10 wherein the wall operates in the elastic regime to transition repeatedly between the first cross-sectional shape and the second cross-sectional shape.
 18. The system of claim 10 further comprising: a pump to circulate the coolant through the cooling tube. 